I've never played 5e and have no preference that way. That said, I find the backstab and high ground rules the biggest detriment to the tactical combat in BG3.
It feels pretty stupid strafing behind the enemy or climbing to elevation in every fight to get a massive accuracy bonus. It's not a tactic, it's a choice and one that's less available to enemies. And the free advantage is so powerful it makes many class abilities irrelevant in comparison.
In a potential PvP scenario, imagine two Fighters doing nothing but backstabs in a 1v1 melee duel. That's how brilliant this system is. Teach the AI to do it too.
Also not a big fan of the excessive jumping, pushing and eating in combat.